Apparatus for injection molding plastic material

Abstract

An apparatus for injection molding thermoplastic material has mold halves carried by stationary and movable mold mounting plates which are mounted on a frame. A control mechanism actively applies a variable torque to one of the mold mounting plates for compensating for any bending of the frame due to the closing force applied between the mold halves.

We claim: 
     
       1. Apparatus for injection molding thermoplastic materials, comprising a substantially C-shaped frame which is bent open by a closing force produced by a closing device between mold halves carried respectively by a stationary and a movable mold mounting plate, wherein an angle between at least one mold mounting plate and an associated limb of the frame is variable, and including a controllable means, connected to the frame for applying to the at least one mold mounting plate a torque for increasing said angle between the at least one mold mounting plate and the associated limb of the frame. 
     
     
       2. Apparatus as set forth in claim 1 wherein the controllable means is in the form of a setting means which is provided with a drive and which actively turns the mold mounting plate into a desired angular position. 
     
     
       3. Apparatus as set forth in claim 2, wherein the setting means is a hydraulic piston. 
     
     
       4. Apparatus as set forth in claim 2, including a hydraulic unit provided in addition to the means for applying the closing force and serving to move the movable mold mounting plate is pivoted to the movable mold mounting plate itself and can be acted upon by pressure during application of the closing force. 
     
     
       5. Apparatus as set forth in claim 4 wherein, during the closing operation, a spring holds the mold mounting plate against the effect of its weight and the rapid-motion stroke cylinder or rapid-motion stroke piston in a normal position. 
     
     
       6. Apparatus as set forth in claim 1, wherein the controllable means is in the form of a releasable abutment which in a fixed condition holds the mold mounting plate parallel to the associated limb of the frame. 
     
     
       7. Apparatus as set forth in claim 6, wherein the abutment is a hydraulic piston. 
     
     
       8. Apparatus as set forth in claim 7, wherein the abutment is acted upon by a motor or a pump. 
     
     
       9. An injection molding machine comprising a closing mechanism having a closing piston and having an end plate wherein the end plate on which a movable mold mounting plate is supported and a stationary mold mounting plate connected exclusively by way of the machine frame, without connecting beam members, and wherein the movable mold mounting plate is mounted tiltably about a horizontal axis so that when a closing force is applied, the movable mold mounting plate is inclined parallel to the stationary mold mounting plate and for that purpose provided on the closing piston is a pivot having an abutment, which connects the closing piston to the movable mold mounting plate, and wherein the closing piston carries at least one support plate and, provided between the movable mold mounting plate and the support plate is a fixing means for temporarily fixing an angular position between the movable mold mounting plate and the support plate. 
     
     
       10. The injection molding machine as set forth in claim 9 including a cylinder connected to the abutment for setting a locking position in a first partial stroke movement of the closing piston and the abutment being movable out of the locking position prior to a second partial stroke movement of the clamping piston.